netdev: convert bulk of drivers to netdev_tx_t

In a couple of cases collapse some extra code like:
   int retval = NETDEV_TX_OK;
   ...
   return retval;
into
   return NETDEV_TX_OK;

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/skge.c b/drivers/net/skge.c
index 543af20..1a1e685 100644
--- a/drivers/net/skge.c
+++ b/drivers/net/skge.c
@@ -2746,7 +2746,8 @@
 		+ (ring->to_clean - ring->to_use) - 1;
 }
 
-static int skge_xmit_frame(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t skge_xmit_frame(struct sk_buff *skb,
+				   struct net_device *dev)
 {
 	struct skge_port *skge = netdev_priv(dev);
 	struct skge_hw *hw = skge->hw;